Black or white?
French Reformed liturgical scholar Richard Paquier: "The Genevan gown, this anti-liturgical, secular vestment, which appears in the color of the shades of darkness, this clothing which is comparable to the sack cloth and ashes of mourning in the old covenant, is the negation of the right of the church to rejoice and be consoled in the presence of the heavenly Bridegroom. Perhaps for the synagogue, in its tribulation, to wear such a vestment would be the normal thing. But in modern Protestantism it is a depressing sign that we are not more aware of the nuptial joy of the Eucharist and that we do not believe in the victorious struggle Christ led against the world." (Dynamics of Worship: Foundations and Uses of Liturgy [Fortress Press, 1967], p. 142).
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Just for the record, Paquier's book is really, really good. If you can find a copy, buy it.